Orthopedic surgeons utilize guide pins for a variety of common procedures, most involving a repair of a joint. For example, when securing a graft in the knee to replace anterior crucial ligament, a guide pin is often used to help create precisely located tunnels for the passage of a graft and/or suture material.
Because the location of such tunnels is critical to the success of any procedure, the guide pins are held along an axis inside of a drill guide or a cannulated reamer, which the drill guide or cannulated reamer is aligned at a specific, desired angle to the joint. The guide pin is then driven by a conventional surgical drill into a first bone, such as the tibia. Once through the tibia, a reamer is often passed over the guide pin to complete the tunnel through the tibia. Afterword, another guide device is often used to axially position the guide pin for passage into a second bone, such as the femur. The conventional surgical drill is then used to drive the guide pin into the femur. Lastly, as is relevant to the present invention, a reamer is then again passed over the guide pin to complete a tunnel through the femur.
As mentioned above, the placement of guide pin is critical, because the ultimate location of the necessary tunnels is a direct result of a proper placement of the guide pins. While the drill guides and other placement devices can be used to accurately determine an initial location and various angle from that placement, once the guide pin enters bone, there is little that can be done to accurately determine the relationship between the distal extent of the guide pin in relation to the extents of the bone or other layers of tissue. Further complicating this is a general inability to accurately determine bone and other tissue thickness in a particular direction along the axis of the desired tunnel.
To aid in the proper placement of the guide pin, certain devices have been invented that allow the surgeon to see graphical representations of a placement. As it is impractical to utilize a real visualization, such as through the use of a magnetic or x-ray device, the graphical visualizations are simulated and based on previously obtained images. As can be easily imagined, such system require highly accurate instrumentation and sensors to know the placement of the surgical instruments and they require perfectly scaled and accurate images of the patients joint for the graphical representation to be functional.
It is also known for a surgeon to merely drive a drill guide by tactile feel and then withdraw the guide pin at times for the purpose of obtaining depth or thickness measurements using traditional measurement tools. While this method is reasonably reliable, it can be time consuming for the removal and replacement of the guide pin and surgical drill, and such a method creates additional clutter in the operating room environment.
The inventors found that placing gradations on the outside of a traditional guide pin failed to provide a suitable measurement regarding a thickness of a tunnel or hole, because once the hole or tunnel is completed, meaning once the guide pin passes entirely through a bone, any gradations starting at the distal end of the guide pin are useless.
Further, the inventors discovered that the mere placement of a proximal facing shoulder near the distal end of the guide pin resulted in problems with accuracy and equipment. For example, the inventor discovered that to create the proximal facing shoulder, the head must be significantly larger than the shaft resulting in a loose fit of the shaft while in a drill guide, cannulated reamer, or an oversized resulting hole due to an oversized head. The inventors discovered that significant accuracy in the placement of the guide pin is lost when using either of these options. Such loss in accuracy would not be tolerated by surgeons or patients.